Patent GB-1006453-A (GB)
Title: Improvements in or relating to electrical recording
IPC: G03G17/02
Filed: 1961-07-28
Abstract: A water-insoluble layer of cellulose acetate phthalate or of a copolymer of methyl methacrylate and methacrylic acid is softened image-wise due to a rise in pH by cathodic action in an aqueous solution of an inorganic salt using an applied potential of 10-100 volts by means of a contacting conductive pattern which may be a photoconductive pattern formed by optical exposure, a moving stylus or a conducting relief printin plate or stencil. The polymeric layers may be coated on paper over a sizing coating from an aqueous solution of gelatin containing potassium chloride, formalin and glycerol.  The softened areas may be transferred to a receiving sheet, e.g. paper, and further treated to form a printing plate; or the differentially hardened polymeric layer may be used as a litho printing plate or wash-off developed to form a relief image.  The polymeric layer may be initially dyed black or the transferred image or wash-off developed relief may be dyed or treated to form a magnetic ink printing plate.ALSO:An image is recorded on a water-insoluble colloid layer of the organic polymeric materials cellulose acetate phthalate or a copolymer of methyl methacrylate and methacrylic acid on a conducting support by contacting the polymeric material with an aqueous solution of an inorganic salt and electrolytically forming by cathodic action an alkaline pattern which solubilizes the polymeric material imagewise.  The imagewise pattern may be produced by a movable stylus, a conducting relief printing plate, a conducting stencil or a photo-conductive material bearing a conductivity image formed by exposure to light (see Divisions B6, G1, G2 and G5).  When using the photoconductive layer electrolytic softening may be effected during or after exposure with an applied potential of 10 to 100 volts.  Typically paper sized with an aqueous gelatin solution containing potassium chloride, formalin and glycerol is coated with a solution in a mixture of ethanol and methoxyethanol of cellulose acetate phthalate containing optionally a black dye and this paper is moistened with an aqueous solution of glycerol and potassium chloride and sandwiched between the gold layer of a "photoelectrode" (see Division H1) as cathode and a counter electrode as anode. Alternatively, the polymeric layer may be formed on the sized paper by coating with an ethanol solution of a methyl methacrylate/methacrylic acid copolymer.  The resultant imagewise solubilized polymeric layer may then be wash-off developed and used either as a relief printing plate or a dye-imbibition printing matrix, or used directly as a litho printing plate or for transferring the solubilized parts to a sheet of paper or simply dyed when the solubilized parts absorb more dye to produce a visible image.  In modifications the methacrylate copolymer layer may contain finely dispersed g -ferric oxide or ferrosoferric oxide or permanent magnet materials and magnetization is effected before or after the electrolytic step, which is itself followed by wash-off development, or after the wash-off development, and the magnetic record is made visible by bathing in a fluorocarbon slurry of carbonyl iron or by means of a magnetic ink or tones powder and this image is then transferred to paper.ALSO:A conducting support, e.g. of metal foil on paper or paper sized with a solution containing gelatin, potassium chloride, formalin and glycerol, is coated with a solution containing cellulose acetate phthalate in ethanol and ethylene glycol monomethyl ether or a solution of a copolymer of methyl methacrylate and methacrylic acid in ethanol.  The polymeric coatings may contain a black dye or ferromagnetic iron oxides.